The invention relates to a plate orifice (restrictor) for a or in a measuring device as well as to measuring devices utilizing said plate orifice for the flow metering of fluid streams, preferably gas streams, in particular for gas streams present in internal combustion engines, with the fluid, in particular the gas, being guided through at least one plate orifice disposed in a pipe and provided with a sharp edge defining its flow orifice and directed radially inwards, with a pressure sensor or pressure measuring line of a differential pressure measuring device or of a differential pressure transducer disposed upstream as well as downstream of the plate orifice, the output signal of the differential pressure measuring device or of the differential pressure transducer depending on the differential pressure forming the measuring signal for the fluid flow rate, in particular gas flow rate, through the plate orifice and optionally being fed to an evaluation unit.
In measuring devices of this type for the flow metering of fluid streams, in particular gas streams, the difference of the measuring signals which are measured by the pressure sensors positioned upstream and downstream of the plate orifice is formed in the differential pressure transducer whose output signal has a designation or characteristic, but not necessarily linear relation to the fluid stream, in particular gas stream, flowing through the plate orifice. As a rule, a simple algorithm exists for determining the rate of flow on the basis of the measuring signal obtained from the differential pressure transducer.